US20040001686A1 - Aerial closure for local convergence point - Google Patents

Abstract

A closure interconnects at least one optical fiber of a feeder cable with two or more optical fibers of a distribution cable at a local convergence point in an optical network. The base of the closure defines a fiber storage and fiber management area adjacent one of the end caps and a fiber coupling area adjacent the other end cap. The fiber coupling area includes one or more coupler modules for splitting an optical signal carried on the optical fiber of the feeder cable into different optical signals carried on the two or more optical fibers of the distribution cable. The optical fiber of the feeder cable is spliced to an input optical fiber of a connectorized pigtail and then split into two or more output optical fibers of connectorized pigtails. The output optical fibers of the pigtails are then spliced to optical fibers of the distribution cable.

Description

FIELD OF THE INVENTION
• The present invention relates generally to enclosures for interconnecting at least one optical fiber of a feeder cable with two or more optical fibers of a distribution cable. More particularly, the invention relates to a closure comprising a plurality of coupler modules for splitting an optical signal carried by an optical fiber of a feeder cable into different optical signals carried on two or more optical fibers of a distribution cable at a local convergence point in an optical network.[0001]
BACKGROUND OF THE INVENTION
• Telecommunications service providers are currently developing networks consisting entirely of fiber optic components to meet the demand for high bandwidth communications service to businesses and homes. These “all-optical” telecommunications networks require a line of service enclosures, referred to herein as “closures,” along the network that are located at access points in the field. Each such location is referred to herein as a “local convergence point.” A closure is utilized at a local convergence point to interconnect optical fibers of a feeder cable from a service provider with optical fibers of one or more distribution cables. In some instances, optical fibers of the feeder cable are connected to optical fibers of drop cables that are routed directly to the business or home of a subscriber of the communications service. In other instances, optical fibers of the feeder cable are connected to optical fibers of a cable that is routed from the closure to yet another local convergence point along the optical network to serve as a further feeder cable for additional drop cables. The further feeder cable is sometimes referred to in the art as a “branch” cable. The optical network may be configured in many different ways, but typically, is configured with a plurality of feeder cables from the service provider having optical fibers that are interconnected with optical fibers of distribution cables at various local convergence points. The distribution cables serve as drop cables routed directly to communications equipment belonging to subscribers, or as branch cables routed to other local convergence points. As used herein, the term “distribution cable” includes both drop cables and branch cables, as those terms are presently understood by one skilled in the art. Furthermore, the term “optical fiber” or “optical fibers” as used herein includes coated and uncoated (i.e., bare) single fibers, jacketed fibers (e.g., tight-buffered and loose buffered), multiple fibers, multiple fiber ribbons, and fiber optic cables containing one or more optical fibers.[0002]
• While fiber optic networks have traditionally served as the back bone or trunk line of telecommunication networks to transmit signals over relatively long distances, all-optical networks are gradually being extended closer to the end points of the network. In this regard, fiber optic networks are being developed that deliver fiber-to-the-home, fiber-to-the-business, fiber-to-the-desk, and the like. In each of these applications, the closure must be capable of interconnecting optical fibers of the feeder cables with optical fibers of the distribution cable to establish the desired optical connections. In existing optical networks, the optical fibers of the feeder cable are typically interconnected with the optical fibers of the distribution cable within a splice closure that is buried underground, mounted in an above-ground pedestal, mounted on a telephone pole, or suspended from an aerial telephone cable strand. In the case of an underground (also referred to as below grade) splice closure, the closure typically includes a frame defining a longitudinal axis that is enclosed by a cylindrical or dome-shaped cover. In the case of a splice closure mounted on a telephone pole or suspended from an aerial telephone cable strand (also referred to as an “aerial closure”), the closure typically includes a base defining a longitudinal axis and a cover movably attached to the base. The cover is intended to protect the optical fiber connections from adverse environmental conditions, while at the same time optimize the number of connections that can be made within the closure. In a splice closure, however, the optical fibers of the feeder cable are spliced in a one-to-one relationship with the optical fibers of the distribution cable. Thus, the number of optical connections that can be made within the splice closure, commonly referred to in the art as the “fiber capacity” of the closure, is limited by the number of one-to-one splices that can be accomplished within the volume constraints of the closure. As the all-optical network proliferates, it is anticipated that the number of optical connections required to be made within the closure will soon exceed the fiber capacity of conventional splice closures.[0003]
• It is further anticipated that demand will require the number of optical fibers of the feeder cable to increase dramatically as the all-optical network proliferates. Since many feeder cables are already installed in fiber optic cable ducts that are buried underground, and because there is oftentimes a physical or functional limit to the number of optical fibers that can be contained together within a feeder cable, there will soon be too few optical fibers from service providers to meet the increased demand for high bandwidth communications service to businesses and homes. It will therefore be necessary, for example, for service providers to install additional feeder cables within existing fiber optic cable ducts or to invest in the construction of additional fiber optic cable ducts to carry the additional feeder cables. In either case, substantial capital expense will have to be incurred by the service provider, and ultimately, passed on to the subscriber in the form of higher cost communications service.[0004]
• As the all-optical network proliferates, there will certainly be an increased need for a field technician to reconfigure the optical connections within the splice closure. Although spliced optical connections can be reconfigured, it is time consuming for the field technician to identify the appropriate optical fibers of the feeder cable and the distribution cable. Furthermore, it generally requires the expertise of a highly trained field technician to reconfigure a conventional splice closure at an access point in the field. As a result, it is costly for a service provider to frequently dispatch a skilled field technician to reconfigure the optical connections within a conventional splice closure. Once again, the additional expense incurred by the service provider to reconfigure the splice closure will ultimately be passed on to the subscriber in the form of higher cost communications service. Accordingly, there is a need for a closure that resolves the aforementioned difficulties associated with the proliferation of an all-optical telecommunications network. The present invention solves these, as well as other, problems by providing a closure for interconnecting at least one optical fiber of a feeder cable with two or more optical fibers of a distribution cable at a local convergence point in an optical network. The closure permits the optical connections to be made in a space efficient, organized and timely manner that does not require a highly skilled field technician to reconfigure the optical connections within the closure.[0005]
BRIEF DESCRIPTION OF THE DRAWINGS
• The present invention will be described in conjunction with the accompanying drawings in which like reference numerals represent the same or similar parts in the different views. The drawings, which are incorporated in and constitute a part of this specification, provide further understanding of the invention, illustrate various embodiments of the invention, and, together with the description, help to fully explain the principles and objectives thereof. More specifically:[0006]
• FIG. 1 is an exploded perspective view of a closure constructed in accordance with the invention for use at a local convergence point in an optical network;[0007]
• FIG. 2 is a perspective view of the interior compartment of the closure of FIG. 1 shown with the distribution fiber slack storage basket and the splice trays of the slack basket and splice tray assembly removed for purposes of clarity;[0008]
• FIG. 3 is a perspective view of the interior compartment of the closure of FIG. 1 shown with the distribution fiber slack storage basket and the distribution fiber splice trays of the slack basket and splice tray assembly removed for purposes of clarity;[0009]
• FIG. 4 is a perspective view of the interior compartment of the closure of FIG. 1 shown with the distribution fiber slack storage basket and the distribution fiber splice trays of the slack basket and splice tray assembly removed for purposes of clarity;[0010]
• FIG. 5 is a perspective view of the interior compartment of the closure of FIG. 1 shown with the slack storage and splice tray assembly and the coupler module assembly fully assembled;[0011]
• FIG. 6 is an exploded perspective view of the closure of FIG. 1 illustrating the interconnection of a typical optical fiber from the feeder cable with a typical optical fiber of the distribution cable;[0012]
• FIG. 7 is a perspective view of a first embodiment of the closure of FIG. 1 illustrating a left-hand cable installation;[0013]
• FIG. 8 is a perspective view of a second embodiment of the closure of FIG. 1 illustrating a right-hand cable installation;[0014]
• FIG. 9 is an exploded rear perspective view illustrating the installation of the coupler module assembly on the back plate; and[0015]
• FIG. 10 is a rear perspective view showing the slack basket and splice tray assembly and the coupler module assembly fully installed on the back plate.[0016]
DETAILED DESCRIPTION OF THE INVENTION
• The invention is described more fully hereinafter with reference to the accompanying drawings, in which various embodiments of the invention are shown. The invention may, however, be embodied in many different forms, and therefore, should not be construed as being limited to the embodiments described and shown herein. Illustrative embodiments are set forth herein so that this description will be thorough and complete, and will fully convey the intended scope of the claimed invention while enabling those skilled in the art to make and practice the invention without undue experimentation.[0017]
• Referring now to FIGS.[0018]1-6, a closure, indicated generally at10, constructed in accordance with one embodiment of the invention is shown. Theclosure10 permits an optical fiber of afeeder cable12 to be interconnected with two or more optical fibers of at least onedistribution cable16 at a local convergence point in an optical network. As used herein, the term “local convergence point” refers to a location along the optical network that provides a field technician with access to the optical connections between thefeeder cable12 and thedistribution cable16. A typical optical network is constructed with a line ofclosures10 along the network that interconnect optical fibers of thefeeder cable12 with optical fibers of drop cables that provide telecommunications services to homes and businesses, or with optical fibers of branch cables leading toother closures10 along the network. Theclosure10 may be buried below ground or disposed in a larger enclosure, such as an above ground pedestal. However, theclosure10 shown and described herein is preferably installed in an aerial location, for example mounted on a telephone pole or hung from an aerial cable strand, and thus, is commonly referred to as an “aerial” closure. Regardless, theclosure10 provides a convenient access point in the optical network for a field technician to initially install and subsequently reconfigure the optical fiber connections between thefeeder cable12 and thedistribution cable16. Although theclosure10 illustrated in the figures is an “in-line” closure, it may have other configurations, such as a canister, or “butt” type closure, or may be a distribution terminal, without departing from the intended spirit or scope of the invention.
• As is well known and understood in the art, the[0019]feeder cable12 may be a main feeder cable from the service provider, or may be a branch cable from a distribution terminal or anotherclosure10 along the optical network. Thefeeder cable12 comprises at least one, and preferably, a plurality of flexible buffer tubes13 (FIGS.2-5) each containing at least one, and preferably a plurality, of optical fibers connected to communications transmission equipment from the service provider. Thedistribution cable16 comprises at least one, and preferably a plurality of flexible buffer tubes17 (FIG. 5). Thedistribution cable16 may comprisebuffer tubes17 for one or more drop cables, each containing at least one optical fiber connected to communications equipment at a subscriber's premises, such as a home or business. Thedistribution cable16 may also comprisebuffer tubes17 for one or more branch cables, each containing at least one optical fiber connected, for example, to anotherclosure10 along the optical network. Thebuffer tubes13 of thefeeder cable12 and thebuffer tubes17 of thedistribution cable16 may contain any type, or types, of optical fibers, such as tight-buffered optical fibers, loose-buffered optical fibers, and ribbon fiber. As such, the term “optical fiber” or “optical fibers” as used herein is intended to include all types of optical transmitting fibers, including individual coated optical fibers, individual uncoated (i.e., bare) optical fibers, tight-buffered optical fibers, loose-buffered optical fibers, optical fibers in the form of a multi-fiber ribbon, or any other known expedient of a light transmitting fiber medium. Additionally, the optical fibers may have various diameters, including for example diameters of 900 micron, 2 mm and 3 mm.
• FIG. 1 is an exploded perspective view showing the various components of the[0020]closure10. As best shown in FIG. 1, theclosure10 comprises a base20 having opposed ends, a pair ofend caps70 attached to the opposed ends of thebase20, and acover80 movably attached to thebase20. Thecover80 is adapted to fit over thebase20 andend caps70 to protect the optical fiber connections within theclosure10 from adverse environmental effects, such as dirt, dust, and insect and rodent infestation, and to provide a relatively water-tight seal with thebase20 andend caps70. As shown herein, thecover80 is hingedly attached to thebase20 for movement between an opened configuration and a closed configuration. Preferably, thebase20 and/or thecover80 comprise conventional fasteners, locking mechanisms, orother means19 for securing thecover80 to the base20 in the closed configuration. In an alternative embodiment, the over80 may be secured on thebase20 by one or more straps comprising “hook and loop” (i.e., VELCRO) type fasteners. Theclosure10 may optionally comprise one ormore hangars90, preferably affixed tobase20, for mounting theclosure10 on a telephone pole or an aerial cable strand in a known manner. Thebase20, end caps70 and cover80 are made of a lightweight, yet structurally rigid material, such as plastic or composite (e.g., fiber and resin material), and preferably, are made of a thermoplastic material, such as polypropylene or polyethylene. However, any relatively lightweight, substantially rigid, flame and fire-resistant, non-porous, and preferably electrically and thermally insulative material is suitable. The remaining structural components of theclosure10 described hereinafter are made of a lightweight, yet rigid metal, such as aluminum. Furthermore, thebase20 may comprise lengthwise and/or lateral (as shown)ribs22 to strengthen and/or stiffen thebase20 of theclosure10 in a desired direction. Thecover80 may likewise comprise lengthwise and/or lateral (as shown)ribs82 to strengthen and/or stiffen thecover80 of theclosure10 in a desired direction.
• The end caps[0021]70 may be attached to the base20 in any conventional manner that permits thefeeder cable12 and thedistribution cable16 to be unsheathed (i.e., a portion of the outer jacket cut and removed) and adequately strain relieved to theend cap70 or thebase20. Eachend cap70 is somewhat disc-shaped and is preferably formed in a one piece that defines a plurality of openings therethrough, referred to herein as cable ports72 (FIGS. 1 and 6), for receiving fiber optic cables. As shown, eachend cap70 has a plurality ofcable ports72 configured to receive thefeeder cable12 and at least onedistribution cable16 therethrough. Typically, one of thecable ports72 will receive thefeeder cable12 and another of thecable ports72 will receive thedistribution cable16. However, any of the remainingcable ports72 may receive anadditional feeder cable12, such as in what is commonly referred to in the art as a “taut-sheath, mid-span application,” or anadditional distribution cable16 comprising one or more drop cables or branch cables. For example, thecable ports72 may receive amain feeder cable12 from the service provider, one or more drop cables leading to a subscriber's premises, such as a home or business, and one or more branch cables leading to anotherclosure10 along the optical network. Thecable ports72 comprise means (not shown) for creating a relatively fluid-tight seal between theend cap70 and thefeeder cable12 and between theend cap70 and eachdistribution cable16. The periphery of theend cap70 is adapted to be received between the interior surface of thebase20 and the interior surface of thecover80, and may be provided with a gasket or other sealing means (not shown). Furthermore, theunused cable ports72 are typically closed off so that thebase20, end caps70, and cover80 define a relatively water-tight enclosure for the optical fiber connections between thefeeder cable12 and thedistribution cable16 housed within theclosure10. The specific configuration of thebase20, the end caps70, and thecover80 is shown for purposes of illustration only, and is not intended to limit the scope of the invention in any way. The design and functionality of thebase20, the end caps70, and thecover80 are known and form no part of the present invention.
• The[0022]base20 is generally elongate and defines a lengthwise direction and a lateral direction. The end caps70 are positioned within the open ends of thebase20 and thecover80 is positioned over the end caps70 and the base20 to define an interior compartment21 (FIG. 1 and FIG. 6) for receiving fiber storage, fiber management, and fiber coupling components therein. Thebase20 is provided with a plurality of mountingposts24 for securing the fiber storage, fiber management, and fiber coupling components within theinterior compartment21 of theclosure10. As shown and described herein, thebase20 defines a fiber storage and fiber management area30 (FIGS.2-5) adjacent theend cap70 receiving theincoming feeder cable12 and the outgoing distribution cable16 (i.e., the left-hand end of the base20 as shown in FIGS.1-6). The base20 further defines a fiber coupling area50 (FIGS.2-5) adjacent the other end cap70 (i.e., the right-hand end of the base20 as shown in FIGS.1-6). The fiber storage andfiber management area30 is preferably located nearer theincoming feeder cable12 and theoutgoing distribution cable16 so as to shorten the lengths of the optical fibers that must be routed within theclosure10. Accordingly, it is less likely that an unprotected optical fiber will be inadvertently bent beyond the allowable limit (e.g., the minimum bend radius) or will be crushed between the base20 and thecover80 when thecover80 is moved relative to the base20 from the opened configuration to the closed configuration. As such, theclosure10 shown and described herein, and in particular the base20, is partitioned into afirst area30 for mounting the fiber storage and fiber management components onto thebase20 and asecond area50 for mounting the fiber coupling components onto thebase20 of theclosure10. As shown, the mountingposts24 are arranged in generally parallel rows of two or more openings spaced along the length of thebase20 and extending in the lateral direction. As a result, the mountingposts24 define a generally planar mounting surface within theinterior compartment21 of theclosure10. Thebase20, however, may be provided with any convenient number of mountingposts24 and the mountingposts24 may be arranged in any suitable configuration. For example, one or more of the mountingposts24 may be deleted, or additional supporting structure may be provided for mounting the fiber storage, fiber management, and fiber coupling components within theinterior compartment21 of theclosure10.
• A[0023]back plate26 is secured to two or more of the mountingposts24 with conventional fasteners or the like. As shown, theback plate26 is generally planar and has a plurality ofopenings25 formed therethrough that receive conventional fasteners or the like to secure theback plate26 to thebase20 and to secure certain of the fiber storage, fiber management, and fiber coupling components to theback plate26, as will be described. Theopenings25 may be through holes or may be internally threaded to accommodate a desired type of fastener. In a particularly advantageous embodiment, the mountingposts24 and theopenings25 receive “push pin” type quick release fasteners so that thebase20, theback plate26, and the fiber storage, fiber management, and fiber coupling components secured to theback plate26 may be quickly and easily connected without the use of tools. As shown and described herein, theback plate26 has a relatively large opening, or cutout,27 (FIGS. 1 and 6) formed therethrough along the lower edge adjacent one end of theback plate26. Theback plate26 is secured within theinterior compartment21 of theclosure10 such that thecutout27 is positioned in thefiber coupling area50 defined by the base20 to receive the fiber coupling components. Thus, thecutout27 of theback plate26 is positioned adjacent theend cap70 that does not receive theincoming feeder cable12 and theoutgoing distribution cable16. One or more buffertube support brackets28 may be secured to theback plate26 to support buffer tubes being routed within theinterior compartment21 of theclosure10. For example, thesupport brackets28 may support one ormore buffer tubes13 of thefeeder cable12 that are being routed through theclosure10 in the aforementioned taut-sheath, mid-span application. Thesupport brackets28 are preferably provided with a plurality of through holes for receiving cable ties, wraps, or the like that contain and secure thebuffer tubes13 to thesupport brackets28. As shown, asingle support bracket28 is provided in the fiber storage andfiber management area30 and asingle support bracket28 is provided in thefiber coupling area50. However, any number ofsupport brackets28 may be provided at one or more convenient locations on theback plate26, as desired.
• The fiber storage and[0024]fiber management area30 houses a slack basket and splicetray assembly32 that is secured to theback plate26 with suitable fasteners that engage certain of theopenings25 provided on theback plate26. In particular, the slack basket and splicetray assembly32 comprises a feeder fiberslack storage basket34 having one ormore brackets35 for securing theslack storage basket34 to theback plate26. Theslack storage basket34 defines a cavity31 (as best shown in FIGS. 1 and 6) for retaining a slack length of fiber optic cable or optical fiber. In particular, theslack storage basket34 retains a plurality of slack lengths of thebuffer tubes13 of thefeeder cable12 between the outer surface of theback plate26 and the inner surface of avertical dividing wall36. Thefeeder cable12 is passed through one of thecable ports72 of thenearest end cap70 and is strain relieved to the base20 or theend cap70 in a known manner, for example by one or more cable ties. A portion of the outer sheath of thefeeder cable12 is removed to expose a suitable length of thebuffer tubes13. Thebuffer tubes13 are routed into the fiber storage andfiber management area30 in any expedient manner that does not exceed the minimum bend radius of the optical fibers within thebuffer tubes13. Theunused buffer tubes13 of thefeeder cable12 are terminated within theclosure10, or are routed from the fiber storage andfiber management area30 out of theclosure10. Preferably, theunused buffer tubes13 are routed out of theclosure10 through the sheathed downstream portion of thefeeder cable12, or through a separate branch cable. Although not shown, the downstream portion of thefeeder cable12 and/or the branch cable exits theclosure10 through one of theother cable ports72 of theend cap70. Theslack storage basket34 preferably comprises at least oneflange37 extending outwardly from the dividingwall36 for retaining the coils of slack lengths ofbuffer tubes13 within thecavity31 between the outer surface of theback plate26 and the inner surface of the dividingwall36. Alternatively, theslack storage basket34 may comprise one or more routing guides, clips, or cable ties to retain the coils of slack lengths ofbuffer tubes13 within thecavity31 defined by theslack storage basket34. As shown, theslack storage basket34 comprises a pair ofbrackets35 that are perpendicular to the dividingwall36 and asingle flange37 that is perpendicular to the dividingwall36 and angled inwardly to retain the coils of slack lengths ofbuffer tubes13 between theback plate26 and the dividingwall36.
• The slack basket and splice[0025]tray assembly32 further comprises one or more splice trays that are mounted outwardly from the dividingwall36 of theslack storage basket34. As shown, theslack storage basket34 further comprises ahorizontal mounting platform38 and a mountingstud39 for supporting the splice trays. Alternatively, the mountingplatform38 may be removed and the splice trays supported on the mountingstud39, or the mountingstud39 may be removed and the splice trays supported on the mountingplatform38. In either instance, the splice trays may be secured to the dividingwall36 by a strap comprising “hook and loop” (i.e., VELCRO) type fasteners. In the embodiments shown and described herein, a single feederfiber splice tray40 and up to three distributionfiber splice trays42, as needed, are supported on the mountingplatform38 and/or the mountingstud39. As shown, each of thesplice trays40,42 has a hole41 (FIGS. 1 and 6) formed therethrough for receiving the mountingstud39, if utilized. Preferably, the feederfiber splice tray40 is positioned nearest to dividing wall36 (and therefore nearest thecavity31 defined by the slack storage basket34) so that the lengths of thebuffer tubes13 of thefeeder cable12 are minimized and the routing of thebuffer tubes13 from thecavity31 to thesplice tray40 is simplified. Conversely, the distributionfiber splice trays42 are positioned farthest from the dividingwall36 for a purpose to be described hereinafter. As shown, thesplice trays40,42 are narrower at one end. In particular, thesplice trays40,42 are narrower adjacent thefiber coupling area50. The narrower end of thesplice trays40,42 facilitates the entry of optical fibers from thebuffer tubes13 of thefeeder cable12 and optical fibers from thebuffer tubes17 of thedistribution cable16 into thesplice trays40,42. The narrower end of thesplice trays40,42 likewise facilitates the exit of optical fibers fromfeeder fiber pigtails14 and optical fibers fromdistribution fiber pigtails18 out ofsplice trays40,42, as will be described hereinafter. As used herein, the term “pigtail” refers to an optical fiber, either bare or jacketed, that has an optical fiber connector on one end. As will be described hereinafter, pigtails14 connect optical fibers from feederfiber splice tray40 tocoupler modules64, whilepigtails18 connect optical fibers from distributionfiber splice trays42 tocoupler modules64. Thesplice trays40,42 are also somewhat smaller in size than conventional splice trays due to the limited amount of space available in the fiber storage andfiber management area30 within theinterior compartment21 of theclosure10. Nevertheless, thesplice trays40,42 are configured to accommodate up to24 separate splices between optical fibers from thebuffer tubes13,17 and optical fibers from the correspondingpigtails14,18.
• The slack basket and splice[0026]tray assembly32 further comprises a distribution fiberslack storage basket44 positioned outwardly of thesplice trays40,42. As shown,slack storage basket44 has a hole45 (FIGS. 1 and 6) formed therethrough for receiving mountingstud39. Theslack storage basket44 may be secured throughhole45 onto the mountingstud39 by a fastener, such as a threaded wing nut. Alternatively, theslack storage basket44 may be secured with thesplice trays40,42 to the dividingwall36 by a strap comprising “hook and loop” (i.e., VELCRO) type fasteners. Theslack storage basket44 similarly defines a cavity43 (FIGS. 1, 5 and6) for retaining a slack length of fiber optic cable or optical fiber. In particular, theslack storage basket44 retains a plurality of slack lengths of thebuffer tubes17 of thedistribution cable16. In yet another embodiment, theslack storage basket44 may be movably attached to the mountingplatform38, for example by a hinge (not shown), so that theslack storage basket44 may be rotated downwardly to provide access to thesplice trays40,42. Accordingly, thesplice trays40,42 may be removed and replaced without disturbing thebuffer tubes17 retained within thecavity43 defined by theslack storage basket44. Thedistribution cable16 is passed through one of thecable ports72 of thenearest end cap70 and is strain relieved to the base20 or theend cap70 in a known manner, for example by one or more cable ties. A portion of the outer sheath of thedistribution cable16 is removed to expose a suitable length of thebuffer tubes17. As shown in FIG. 5, thebuffer tubes17 are routed into the fiber storage andfiber management area30 to theslack storage basket44 such that the slack lengths ofbuffer tubes17 are retained within thecavity43 defined by theslack storage basket44. Thebuffer tubes17 are routed into the fiber storage andfiber management area30 in any expedient manner that does not exceed the minimum bend radius of the optical fibers within thebuffer tubes17. Theunused buffer tubes17 of thedistribution cable16 are terminated within theclosure10. Theslack storage basket44 preferably comprises at least one outwardly extendingflange47 for retaining coils of the slack lengths ofbuffer tubes17 within thecavity43 defined by theslack storage basket44. Alternatively, theslack storage basket44 may comprise one or more routing guides, clips, or cable ties to retain coils of the slack lengths ofbuffer tubes17 within thecavity43 defined by theslack storage basket44. As shown, theslack storage basket44 comprises a pair offlanges47 that are perpendicular to the planar surface of theslack storage basket44 in the lengthwise direction, and a pair ofsmaller flanges47 that are perpendicular to the planar surface of theslack storage basket44 in the lateral direction to retain the coils of slack lengths ofbuffer tubes17 within thecavity43 defined by theslack storage basket44. Preferably, the distributionfiber splice trays42 are positioned farthest from the dividing wall36 (and therefore nearest thecavity43 defined by the slack storage basket44) so that the lengths of thebuffer tubes17 of thedistribution cable16 are minimized and the routing of thebuffer tubes17 from theslack storage basket44 to thesplice trays42 is simplified.
• The[0027]fiber coupling area50 houses acoupler module assembly52 that is secured to theback plate26 with suitable fasteners that engage certain of theopenings25 provided on theback plate26. In particular, thecoupler module assembly52 comprises acoupler module housing54 and one ormore brackets55 for movably attaching thecoupler module housing54 to theback plate26. Thecoupler module housing54 defines an interior cavity53 (FIGS. 1 and 6) for retaining a plurality of coupler modules64 (FIGS.2-5), as will be described. As shown, thecoupler module housing54 has one or moreelongate slots57 formed in eachend wall58, and eachbracket55 comprises one or more guide pins56 that engages theslot57. Thecoupler module housing54 further comprises aflange60 extending outwardly from eachend wall58 that has ahole59 formed therethrough. Thehole59 receives a fastener, such as a conventional quarter-turn fastener, therethrough that engages a correspondinghole51 provided on thebracket55 to lock thecoupler module housing54 to thebracket55 in a closed position. When the fastener releases thecoupler module housing54 from thebracket55, theslot57 of thecoupler module housing54 is slidable on the guide pins56 so that thecoupler module housing54 is movable relative to thebracket55 from the closed position to an opened position. In the opened position, thecoupler modules64 are accessible to make optical connections between thepigtails14,18 spliced to optical fibers from thebuffer tubes13,17 of thefeeder cable12 and thedistribution cable16, respectively, and thecoupler modules64, as will be described. Theslot57 and guide pins56 also prevent thecoupler module housing54 from being detached from thebracket55 and removed from thefiber coupling area50. If thecoupler module housing54 is inadvertently removed, thepigtails14,18 and/or the optical connections between thepigtails14,18 and thecoupler modules64 may be damaged. Thecoupler module housing54 can be fixed to thebrackets55 or theback plate26 to prevent possible damage to thepigtails14,18 and the optical connections. However, access to the optical connections, and particularly those connections located nearest to theback plate26, would be significantly reduced.
• The[0028]coupler module assembly52 further comprises a pigtailslack storage basket66 that is secured to thecoupler module housing54 by one ormore brackets65. Preferably, abracket65 is provided adjacent eachend wall58 of thecoupler module housing54 so that the pigtailslack storage basket66 can be located at either lengthwise end of thecoupler module housing54, for a purpose which will become evident hereinafter. Eachbracket65 comprises an outwardly extendingflange62 that has one or more holes formed therethrough. The pigtailslack storage basket66 has a corresponding hole formed therethrough for receiving a fastener to secure the pigtailslack storage basket66 to thebracket65. As shown, the pigtailslack storage basket66 has a pair of lengthwise extendingflanges67 and a pair of guide rings68 (FIG. 1) for retaining thepigtails14,18 within the pigtailslack storage basket66. Thecoupler module assembly52 further comprises a couplermodule housing cover69 for protecting thecoupler modules64 and thepigtails14,18 that are routed between the fiber storage andfiber management area30 and thefiber coupling area50. The couplermodule housing cover69 has one or more holes for receiving a fastener, such as a conventional quarter-turn fastener, therethrough that engages a correspondinghole61 provided on thebracket65 to lock the couplermodule housing cover69 to thebracket65. Preferably, the couplermodule housing cover69 comprises awindow69amade of a transparent material, such as LEXAN, so that the optical connections between thepigtails14,18 and thecoupler modules64 can be observed without removing the couplermodule housing cover69.
• FIG. 2 is a perspective view of the[0029]interior compartment21 of theclosure10 with the distribution fiberslack storage basket44, the feederfiber splice tray40, and the distributionfiber splice trays42 removed for purposes of clarity. As shown in FIG. 2, thebuffer tubes13 of thefeeder cable12 positioned in theend cap70 are routed into the fiber storage andfiber management area30. Thebuffer tubes13 are routed to thecavity31 defined by the feeder fiberslack storage basket34 where coils of slack lengths of thebuffer tubes13 are retained between theback plate26 and the dividingwall36. As previously mentioned,unused buffer tubes13 may be terminated in thecavity31, or may be directed out of theclosure10 through the downstream feeder cable or a separate branch cable.
• FIG. 3 is a perspective view of the[0030]interior compartment21 of theclosure10 with the distribution fiberslack storage basket44 and the distributionfiber splice trays42 removed for purposes of clarity. As shown in FIG. 3, one of thebuffer tubes13 of thefeeder cable12 is routed from thecavity31 defined by theslack storage basket34 to thesplice tray40 where suitable lengths of the optical fibers from thebuffer tube13 are further routed into thesplice tray40.
• FIG. 4 is a perspective view of the[0031]interior compartment21 of theclosure10 with the distribution fiberslack storage basket44 and the distributionfiber splice trays42 removed for purposes of clarity. Inside thesplice tray40, optical fibers from thebuffer tube13 are spliced one-to-one in a known manner to input optical fibers fromfeeder fiber pigtails14. As shown in FIG. 4, the correspondingpigtails14 are routed from thesplice tray40 to the pigtailslack storage basket66 where coils of the slack lengths of thepigtails14 are retained by theflanges67 and guide rings68 within theslack storage basket66. Thepigtails14 are then routed from theslack storage basket66 to apredetermined coupler module64 housed within thecoupler module housing54. The connectorized ends of thepigtails14 are optically connected toconventional adapters64aprovided on thecoupler module64.
• FIG. 5 is a perspective view of the interior compartment of the[0032]closure10 with the slack storage andsplice tray assembly32 and thecoupler module assembly52 fully assembled. Inside thecoupler module64, the optical fiber from eachpigtail14 is split in a known manner into two or more output optical fibers fromdistribution fiber pigtails18 that carry different optical signals than the optical signal carried by the optical fiber from thepigtail14. As shown in FIG. 5, the connectorized ends of thepigtails18 are optically connected toadapters64aprovided on thecoupler module64. Thepigtails18 are routed from thecoupler module64 to the pigtailslack storage basket66 where coils of the slack lengths of thepigtails18 are retained by theflanges67 and guide rings68 within theslack storage basket66. Thepigtails18 are then routed from theslack storage basket66 to the distributionfiber splice trays42. Inside thesplice trays42, output optical fibers from thepigtails18 are spliced one-to-one in a known manner to optical fibers from thebuffer tubes17 of thedistribution cable16. Thebuffer tubes17 of thedistribution cable16 are then routed from thesplice trays42 to the distribution fiberslack storage basket44 where coils of the slack lengths of thebuffer tubes17 are retained byflanges47 within thecavity43 defined by theslack storage basket44. Finally, thebuffer tubes17 are routed from theslack storage basket44 in the fiber storage andfiber management area30 to thedistribution cable16 positioned in theend cap70.
• FIG. 6 is an exploded perspective view of the[0033]closure10 that illustrates the interconnection of a typical optical fiber of thebuffer tube13′ of thefeeder cable12 with at least two typical optical fibers of thebuffer tubes17′ of thedistribution cable16. As previously described, thebuffer tube13′ is routed to theslack storage basket34 and thereafter to thesplice tray40 where the optical fiber from thebuffer tube13′ is spliced to the input optical fiber of thepigtail14′. Thepigtail14′ is then routed to theslack storage basket66 and thereafter to thepredetermined coupler module64. The input optical fiber is split inside the coupler module into at least two output optical fibers of thepigtails18′. Thepigtails18′ are routed to theslack storage basket66 and thereafter to thesplice trays42 where the output optical fibers of thepigtails18′ are spliced to optical fibers from thebuffer tubes17′. Thebuffer tubes17′ then exit theclosure10 throughdistribution cable16. The configuration illustrated in FIG. 6 is typically utilized to permit a field technician to field terminate selected optical connections by interconnecting and mechanically splicing at least one input optical fiber of apigtail14′ frombuffer tube13′ offeeder cable12 with two or more output optical fibers ofpigtail18′ frombuffer tubes17′ ofdistribution cable16, for example drop cables or branch cables, through one ormore coupler modules64 provided withinfiber coupling area50 and one ormore splice trays40,42 provided within fiber storage andfiber management area30.
• FIG. 7 is a perspective view of a first embodiment of the[0034]closure10 illustrating a left-hand cable installation. In particular, thefeeder cable12 and thedistribution cable16 pass through theend cap70 on the left-hand side of thebase20. Accordingly, theback plate26 is mounted within theinterior compartment21 such that the fiber storage andfiber management area30 is on the left and thefiber coupling area50 is on the right. FIG. 8 is a perspective view of a second embodiment of theclosure10 illustrating a right-hand cable installation. In particular, thefeeder cable12 and thedistribution cable16 pass through theend cap70 on the right-hand side of thebase20. Accordingly, theback plate26 is mounted within the interior compartment21 (i.e., flipped over about the lateral axis) such that the fiber storage andfiber management area30 is on the right and thefiber coupling area50 is on the left. FIGS. 7 and 8 show the fiber storage andfiber management area30 and thefiber coupling area50 of a fullypopulated closure10 wherein a total of18 optical fibers from asingle buffer tube13 of thefeeder cable12 are spliced inside feederfiber splice tray40 to a corresponding total of18 input optical fibers ofpigtails14. The18 input optical fibers frompigtails14 are then split by ninecoupler modules64 into a total of 72 output optical fibers ofpigtails18. The 72 output optical fibers frompigtails18 are then spliced inside distributionfiber splice trays42 to a corresponding total of72 optical fibers ofdistribution cable16. The configuration shown in FIGS. 7 and 8 is for illustration purposes only, and theclosure10 may be configured to have any convenient number offeeder cables12,buffer tubes13,splice trays40,pigtails14,coupler modules64,pigtails18,splice trays42,buffer tubes17, anddistribution cables16. Furthermore, theclosure10 may be configured initially with fewer than all of thesplice trays40,42 andcoupler modules64, andadditional splice trays40,42 andcoupler modules64 may be installed later as the remaining capacity of theclosure10 permits. Furthermore, thecoupler modules64 may be mounted in thecoupler module housing54 at a angle relative to the lengthwise direction defined by the base20 so as to provide improved access to the optical fiber connections, or to provide increased capacity.
• FIG. 9 is an exploded rear perspective view illustrating the installation of the[0035]coupler module assembly52 on theback plate26. FIG. 10 is a view from the same perspective showing the slack basket and splicetray assembly32 and thecoupler module assembly52 fully installed on theback plate26. Thefiber coupling area50 comprises a plurality ofcoupler modules64 retained in acavity53 defined by thecoupler module housing54 that is attached to thebase20 bybrackets55. As shown, eachcoupler module64 is oriented vertically relative to the base20 (i.e., parallel to the lateral direction defined by the base20) and parallel to the end caps70. Eachcoupler module64 is attached to the upper edge of thecoupler module housing54 such that thecoupler module64 extends inwardly into thecavity53 defined by thecoupler module housing54. In the embodiments shown and described herein, a total of ninecoupler modules64 may be retained within thecavity53 defined by thecoupler module housing54. Preferably, each of thecoupler modules64 is secured to the upper edge of thecoupler module housing54 by ahook63 at one end and a latch plunger (not shown) at the opposite end. The upper edge of thecoupler module housing54 is provided with acomplimentary opening63afor receiving thehook63 and a complimentary latch grommet (not shown) on the opposite side for receiving the latch plunger. Thecoupler module64 is inserted into thecavity53 defined by thecoupler module housing54 such that thehook63 is received within the correspondingopening63aformed in the upper edge of the coupler module housing54 (FIG. 9). Thecoupler module64 is then moved in a direction generally perpendicular to both the lengthwise direction and the lateral direction defined by the base20 away from theback plate26 until the latch plunge overlies the latch grommet provided on the opposite side of the upper edge of thecoupler module housing54. Thecoupler module64 is then moved in a direction generally perpendicular to the lengthwise direction and generally parallel to the lateral direction defined by thebase20 until the latch plunger engages the latch grommet. Thecoupler module64 may be removed from thecoupler module housing54 by pulling the latch plunger upwardly and reversing the above steps.
• As previously mentioned, each[0036]coupler module64 divides, or splits, an optical signal carried on an input optical fiber of afeeder fiber pigtail14 spliced to an optical fiber from abuffer tube13 offeeder cable12 into different optical signals carried on two or more output optical fibers ofdistribution fiber pigtails18 spliced to buffertubes17 ofdistribution cable16. Preferably, eachcoupler module64 has a plurality ofadapters64afor receiving input optical fibers (i.e., pigtails14) and output optical fibers (i.e., pigtails18) having fiber optic connectors on at least one end. Thus, the input optical fibers and the output optical fibers are referred to herein as “pre-connectorized” or “connectorized.” Theadapters64amay be staggered, or angled, or both, relative to thecoupler module64 to likewise provide improved access to the connectors or increased fiber capacity. As shown, eachcoupler module64 comprises a total of tenadapters64afor receiving connectorized optical fibers. As a result, eachcoupler module64 hasenough adapters64ato split input optical fibers from a pair ofpigtails14 into two sets of output optical fibers from four pigtails18 (i.e., a pair of 1×4 couplers). Alternatively, eachcouple module64 may split one input optical fiber from asingle pigtail14 into output optical fibers from eight pigtails18 (i.e., a single 1×8 coupler).
• Preferably, the innermost two[0037]adapters64aare available to receive input optical fibers frompigtails14 spliced to buffertube13 offeeder cable12, while the outermost eightadapters64aare available to receive output optical fibers frompigtails18 spliced to buffertubes17 ofdistribution cable16. This configuration permits the optical fibers to be positioned in a predetermined sequence within thecoupler modules64. Theclosure10 can be configured initially to comprise anywhere from one to ninecoupler modules64, andadditional coupler modules64 may be added later as the remaining capacity of theclosure10 permits. Thus, when fully populated with nine coupler modules64 (as shown in FIGS. 7 and 8), theclosure10 permits up to 18 input optical fibers frompigtails14 to be split into up to 72 output optical fibers frompigtails18. As previously described, the 72 output optical fibers frompigtails18 may be individual drop cables leading to homes or businesses, or may be branch cables leading toother closures10 along the optical network, or may be both. Thepigtails14,18 may be uncoated (i.e., bare) individual fibers, but preferably, are coated with a plastic sheath to protect the optical fibers from adverse environmental effects. Furthermore, thepigtails14,18 may be color-coded to permit ready identification. Preferably, each of thepigtails14,18 is about the same length for ease of manufacture and installation. Slack lengths of thepigtails14,18 are retained within theslack basket66 so that the appropriate length of thepigtail14,18 may be routed to thefiber coupling area50 and to the fiber storage andfiber management area30, respectively.
• The illustrative embodiments of the closure shown and described herein provide a number of significant advantages over previously known closures, such as conventional splice closures. For purposes of example only, and not by way of limitation, a closure constructed in accordance with the invention provides substantially greater capacity than a conventional splice closure as a result of the incorporation of coupler modules. Furthermore, a closure constructed in accordance with the invention provides substantially greater capacity as a result of the efficient use of the space available within the closure for the fiber storage, fiber management, and fiber coupling components. Still further, a closure constructed in accordance with the invention provides a field technician with substantially greater ease and flexibility in re-configuring the optical fiber connections within the closure. Still further, a closure constructed in accordance with the invention permits an optical fiber from a feeder cable to be interconnected with two or more optical fibers of a distribution cable. In an alternative embodiment, one or more of the splice trays may be removed from the closure to permit a technician to field terminate at least one pre-connectorized optical fiber from a feeder cable with two or more pre-connectorized optical fibers from a distribution cable, or with two or more optical fibers from a distribution cable through at least one mechanical splice tray.[0038]
• Many modifications and other embodiments of the invention will come to mind to one skilled in the art to which this invention pertains having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the invention is not to be limited to the specific embodiments disclosed herein and that further modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.[0039]

Claims (27)

That which is claimed is:

1. A closure for interconnecting at least one optical fiber of a feeder cable with two or more optical fibers of a distribution cable, the closure comprising:

a base defining a lengthwise direction and a lateral direction;

at least one end cap attached to the base, the end cap having at least one opening therethrough for receiving the feeder cable and at least one opening therethrough for receiving the distribution cable;

a fiber storage and fiber management area for storing slack lengths of the optical fiber of the feeder cable and slack lengths of the optical fibers of the distribution cable and for splicing the optical fiber of the feeder cable and the optical fibers of the distribution cable to optical fiber pigtails; and

a fiber coupling area for splitting an optical signal carried by the optical fiber pigtail spliced to the optical fiber of the feeder cable into two or more optical signals carried by the optical fiber pigtails spliced to the optical fibers of the distribution cable.

2. A closure according toclaim 1 wherein the fiber coupling area comprises a plurality of coupler modules removably attached to a coupler module housing.

3. A closure according toclaim 2 wherein the optical fiber pigtails are connectorized and wherein each of the coupler modules comprises a plurality of adapters for receiving the connectorized optical fiber pigtails.

4. A closure according toclaim 2 wherein the coupler module housing defines a cavity and each of the coupler modules is retained within the cavity such that the coupler module is perpendicular to the lengthwise direction defined by the base.

5. A closure according toclaim 2 wherein each of the coupler modules comprises a hook that is received within an opening formed in the coupler module housing to removably attach the coupler module to the coupler module housing.

6. A closure according toclaim 1 wherein the fiber storage and fiber management area comprises at least one slack storage basket and at least one splice tray.

7. A closure according toclaim 6 wherein the at least one slack storage basket comprises a feeder fiber slack storage basket for retaining slack lengths of the optical fiber of the feeder cable and a distribution fiber slack storage basket for retaining slack lengths of the optical fibers of the distribution cable.

8. A closure according toclaim 7 wherein the splice tray is positioned between the feeder fiber slack storage basket and the distribution fiber slack storage basket.

9. A closure according toclaim 7 further comprising a back plate secured to the base and wherein the feeder fiber slack storage basket is secured to the back plate, the splice tray is positioned outwardly of the feeder fiber slack storage basket, and the distribution fiber slack storage basket is positioned outwardly of the splice tray.

10. A closure according toclaim 7 wherein each of the feeder fiber slack storage basket and the distribution fiber slack storage basket comprise at least one flange for retaining the slack lengths of the optical fiber of the feeder cable and the slack lengths of the optical fibers of the distribution cable.

11. A closure according toclaim 1 wherein the fiber storage and fiber management area is located adjacent the end cap and the fiber coupling area is located adjacent the fiber storage and fiber management area in the lengthwise direction defined by the base.

12. A closure according toclaim 1 wherein the fiber storage and fiber management area comprises a feeder fiber splice tray for splicing the optical fiber of the feeder cable to one of the optical fiber pigtails and at least one distribution fiber splice tray for splicing the optical fibers of the distribution cable to others of the optical fiber pigtails.

13. A closure for interconnecting an input optical fiber with a plurality of output optical fibers, the closure comprising:

a base defining a lengthwise direction and a lateral direction;

at least one end cap attached to the base, the end cap having at least one opening therethrough for receiving the input fiber and at least one opening therethrough for receiving the output fibers;

a back plate secured to the base and having opposed ends in the lengthwise direction;

a fiber storage and fiber management area adjacent one of the opposed ends of the back plate for storing slack lengths of the input optical fiber and slack lengths of the output optical fibers;

a fiber coupling area adjacent the other opposed end of the back plate for splitting an optical signal carried by the input optical fiber into a plurality of optical signals carried by the output optical fiber.

14. A closure according toclaim 13 wherein the fiber coupling area comprises a plurality of coupler modules removably attached to a coupler module housing.

15. A closure according toclaim 14 wherein the input optical fiber and the output optical fibers are connectorized and wherein each of the coupler modules comprises a plurality of adapters for receiving the connectorized input optical fiber and the connectorized output optical fibers.

16. A closure according toclaim 14 wherein the coupler module housing defines a cavity and each of the coupler modules is retained within the cavity such that the coupler module is perpendicular to the lengthwise direction defined by the base.

17. A closure according toclaim 14 wherein each of the coupler modules comprises a hook that is received within an opening formed in the coupler module housing to removably attach the coupler module to the coupler module housing.

18. A closure according toclaim 13 wherein the fiber storage and fiber management area comprises at least one slack storage basket.

19. A closure according toclaim 18 wherein the at least one slack storage basket comprises a feeder fiber slack storage basket for retaining slack lengths of the input optical fiber and a distribution fiber slack storage basket for retaining slack lengths of the output optical fibers.

20. A closure according toclaim 19 wherein the feeder fiber slack storage basket is secured to the back plate and positioned outwardly therefrom and the distribution fiber slack storage basket is positioned outwardly of the feeder fiber slack storage basket.

21. A closure according toclaim 19 wherein each of the feeder fiber slack storage basket and the distribution fiber slack storage basket comprise at least one flange for retaining the slack lengths of the input optical fiber and the slack lengths of the output optical fibers.

22. A closure according toclaim 13 wherein the fiber storage and fiber management area is located adjacent the end cap and the fiber coupling area is located adjacent the fiber storage an fiber management area in the lengthwise direction defined by the base.

23. A closure according toclaim 13 wherein the fiber storage and fiber management area comprises at least one splice tray for splicing the input optical fiber and the output optical fibers to a plurality of optical fiber pigtails.

24. A closure according toclaim 13 wherein the input optical fiber is a pre-connectorized feeder cable and the output optical fibers are pre-connectorized drop cables.

25. A closure for interconnecting an input optical fiber with a plurality of output optical fibers, the closure comprising:

a base defining a lengthwise direction and a lateral direction; and

a coupler module housing attached to the base, the coupler module housing defining a cavity for receiving at least one coupler module for splitting an optical signal carried on the input optical fiber into a plurality of optical signals carried on the output optical fibers.

26. A closure according toclaim 25 further comprising at least one bracket secured to the base and wherein the bracket comprising at least one guide pin and the coupler module housing has a slot for receiving the guide pin so that the coupler module housing is movable relative to the base and the bracket.

27. A closure according toclaim 26 wherein the coupler module housing is slidably attached to the bracket so that the coupler module housing is movable relative to the base in a direction perpendicular to both the lengthwise direction and the lateral direction.

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